Directing against the problems existing in many power plants

i.e.the bypass system of units is unable to bring its protective effects into full play

and only used as a drain valve of boiler and steam turbine in the stage of start-up or shutdown of units

a new bypass control strategy has been designed

which devides the HP-bypass into five control modes

the whole process automatic control of bypass system

from start-up of unit to connet the unit onto power grid

and returned again to sectionalization and shutdown of boiler

can be realized.Through calculation of steam's enthalpy drop before and after the LP-bypass system

the quantity of desuperheating water required by the LP-pass system can be precisely pre-estimated

thereby the exhaust steam from the LP-bypass system can be ensured to satisfy the requirement in operation of condenser.The above-mentioned control strategy has been applied onto an ultra-supercritical 1 000 MW unit in second-phase project of Ninghai Power Plant

the fast cut back (FCB) of unit without boiler shutdown being realized;after finishing assessment test of the bypass system

the unit is reconnected onto the power grid within 0 min

and the load of unit being increased to 480 MW after 15 min.